Just William - the first in a series of children's books by Richmal Crompton. I think they first apppeared in the 1920's, but continue to be popular today.

The following is courtesy of Amazon:
Book Description
"There is only one William. This tousle-headed, snub-nosed, hearty, loveable imp of mischief has been harassing his unfortunate family for over 20 years. He's as famous over radio as he is in print. His name is a byword for irrepressible boyhood. His pranks are the scrapes of every healthy youngster, recorded with keen observation and an even keener sense of humour by one of our brightest writers. He is-- just William!" --From the jacket of an edition from the 1940s.